A target wheel is a disk that is engaged with a vehicle crankshaft and that is configured for inducing signals in one or more sensors positioned next to the target wheel, with the signals representing the angular position of the crankshaft. These position signals can be used in distributorless ignition systems that have selectively energized ignition coils that fire the spark plugs as appropriate for the angular position of the crankshaft. Moreover, the crankshaft angular position signals can be used for combustion control and diagnostic functions.
Examples of target wheels are set forth in, e.g., U.S. Pat. No. 5,754,042, incorporated herein by reference, and in co-pending U.S. patent application Ser. No. 09/250,826, filed Feb. 17, 1999, also incorporated herein by reference. Essentially, the edge of the disk-shaped wheel is varied along the periphery of the wheel in some fashion, e.g., by cutting slots in the periphery in a predetermined pattern. Usually, one or two sensors are used to detect the slots as they pass by the sensors, with the detected slot pattern being correlated to a crankshaft angular position and, when two sensors are used, also to a crankshaft direction of rotation. Unfortunately, when two sensors are used instead of one, as currently must be done to sense direction of crankshaft rotation, the cost and complexity of such systems is increased. The present invention has recognized the above-noted problems and has provided the below solutions to one or more of the above-noted problems.